Leeoy b



(No Model.)

L. B. ERMAN. A CENTRAL OFFICE APPARATUS XFOR TELEPHONES.

Patented Aug. 14, 1883.

s E E UNITED STATES LEROY B. FIRMAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERN ELECTRIC COMPANY, OF SAME PLACE.

CENTRAL-OFFICEAPPARATUS FOR TELEPHONES.

SPECIFICATION forming part of Letters Patent No. 283,334, dated August 14, 1883.

Application filed March 16, 1881. (No model.)

My invention is shown in the drawing.r

A, B, and C represent connecting-plates on Y the switch-board at the central ofiice.

D is the operators telephone-outfit. VE is a peg-switch.

L, L?, and L3 represent the respective lines of three subscribers, whom we will designate as S, S2, and The telephone-line of each subscriber, when not in use, passes through an annunciator-number and two Abolts and to ground at the central office. Thus S2 is con nected by his line LE with annunciator-number 2 and thence to bolt b, and by the plugs and iiexible conducting-cord, to bolt b', and thence to ground, as shown. l The subscribers, signal the central ofiice,when they wish to be connected through the central office, by sen ding currents along their telephone-lines. Thus if S2 should send a current along line L2 the shutter of his annunciator 2 would be released, and by this signal the switchman would know that S2 wished to talk with some one. W'hen the switchnian sees a shutter fall he takes oii the ground by pulling out a plug from one of the two bolts in the circuit of the subscriber who has sent in the call. The switchman then connects the connecting-plate of the line of the subscriber with the operator7 s telephone through the peg-switch. In the drawing the plugs that belong in bolts c and c are thus .removed or pulled out and are allowed io hang, as shown.

The connection between the subscriber and operator may be traced as follows, and suppose that plug o has not been inserted in the bolt o: From the subscribers station in the usual manner to the central office byline L to plate A, thence by plug m and its cord to plate f of the peg-switch, and thence through the medium of aplug not shown in the drawings) to plate d, and thence through the operators telephone-outt D in the usual manner, and to ground, as shown. S, when thus connected with the operator at the central office, informs him of what connection he desires. For example, suppose S should ask to be connected with S3, The switchman is informed of the fact, and thereupon inserts plug n in plate C, and takes off the ground by pulling out the plug from bolt c, as shown. A plug is inserted connecting the pla-tesV c and f of the peg-switch. The subscribers S and S3 arethus connected with each other and with the operators telephone-outfit. The operator by throwing his battery to line calls up S3, and at the saine time informs S that he`is doing his duty. Vhen the subscribers have begun their conversation the operator informs the switchinan, who thereupon inserts plug p in plate C, and plug o in bolt c and pulls out the plugs m and n. The work of the operator is now complete and he is free to attend to another call.

The subscribersSand S are shown connected through annunciator l, as follows: By line L3 to plate C, thence by plugs p and o and their conducting-cord to bolt a, thence through annunciator l to line L. When Sr and S are through talking, either, by throwing his battery to line, may throw down the shutter of annunciator l, and then the switchman pulls out the plugs o and p and restores the hanging plugs to bolts a ande.

It will be seen that the two subscribers will I also be connected with each other through an annunciator if the plug p should be inserted in switch or plate A and plug o in bolt c.

I claiml. The combination of telephone-lines VL and L3 with connecting-plates A C, each provided with two plug-bales, the branch circuits, including annunciators l and 8, and switching apparatus, as described, whereby either of said annunciators may be included in the circuit of said telephone-lines whenconnected, as and for the purpose specified.

2. The combination ofthe telephone-lines with switches, one for each line upon the central-oflice switch-board, branch circuits, one branch circuit for each line, each branch including an annunciator and switching apparatus, -whereby any two telephone-lines may be connected together through the annunciator of one of the lines, while the annunciator of the other line is not included-in the circuit.

LEROY B.. FIRMAN.

IOO 

